This invention relates to metal-air batteries.
Batteries are commonly used electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an active material that can be oxidized; the cathode contains or consumes an active material that can be reduced. The anode active material is capable of reducing the cathode active material. In order to prevent direct reaction of the anode material and the cathode material, the anode and the cathode are electrically isolated from each other by a separator.
When a battery is used as an electrical energy source in a device, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte, for example, potassium hydroxide, in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
In a metal-air electrochemical cell, oxygen is reduced at the cathode, and a metal is oxidized at the anode. Oxygen is supplied to the cathode from the atmospheric air external to the cell through one or more air hole(s) in the cell can. To prolong battery life, it is desirable that the cathode be exposed to air flow when in use, and isolated from air flow when not in use.
The invention relates to a metal-air battery cartridge that, when used in a device, provides good air management according to the power requirements of the device. Generally, the cartridge seals a battery inside the cartridge from air when the device is off and exposes the battery to air when the device is on.
In certain devices requiring batteries, such as in some cellular telephones, the batteries are not subject to continuous use. Rather, the batteries are subject to intermittent use in which the batteries cycle between an xe2x80x9coffxe2x80x9d mode and an xe2x80x9conxe2x80x9d mode of operation. During the off mode, no current is drawn from the batteries; and during the on mode, the maximum current may be drawn. Some telephones also have a xe2x80x9cstandbyxe2x80x9d mode of operation in which a non-maximum amount of current is drawn.
During the periods of time when these devices are not on, it is desirable to limit or restrict the amount of air that enters the batteries. Overexposure to air can lead to premature degradation of the materials in the batteries. For example, carbon dioxide can react with a potassium hydroxide electrolyte to form potassium carbonate. This can lead to poor battery performance and a reduced battery life.
In one aspect, the invention features a battery cartridge including a casing, a battery in the casing, and a slide moveably engaged with the casing. The battery includes an opening, and the slide includes an opening alignable with the opening of the battery.
Embodiments may include one or more of the following features.
The slide can be moveable between a first position in which the opening of the slide is aligned with the opening of battery, and a second position in which the opening of the slide is misaligned with the opening of battery. The slide can be further moveable to a third position in which the opening of the slide is partially aligned with the opening of the battery. The casing can define a groove, and the slide can be moveably engaged in the groove.
The slide can further include at least one latch, which can retain the slide at a predetermined engagement position with the casing. The latch can be integrally molded in the slide.
The cartridge can further include an auxiliary power source adapted to move the slide. The auxiliary power source can be a second battery.
The casing can have a prismatic shape, e.g., a rectangular prism and a circular prism.
The battery can have a rectangular cross section. The battery can be a metal-air battery, e.g., one that includes a cathode having manganese dioxide and an anode having zinc.
In another aspect, the invention features an electrochemical power source having a metal-air battery system including an opening and air control member arranged for relative sliding motion to variably cover the opening for controlling exposure to an oxygen-containing environment.
In another aspect, the invention features an electrochemical power source having a metal-air battery system including a pair of openings in parallel planar arrangement. The openings are arranged for variable alignment to control exposure to an oxygen-containing environment.
The battery cartridge provides a simple and functional system for managing air flow into a metal-air battery. The cartridge can be formed in a variety of shapes to suit different devices, and the cartridge can be produced at a low cost. Operation of the cartridge is simple. In some embodiments, operation of the cartridge is transparent to the user.
A prismatic battery can be generally rectangularly shaped. For example, a prismatic battery can be relatively flat with two parallel rectangularly-shaped faces, making them suitable for use in cellular telephones. More broadly, a prismatic battery can be shaped as a polyhedron with two polygonal faces lying in parallel planes and with the other faces, if any, as parallelograms. For example, if the polygonal faces are rectangular, then the battery is shaped as a rectangular prism. If the polygonal faces are circular, then the battery is shaped as a circular prism. Prismatic batteries can be efficiently and conveniently stacked together, e.g., in a cellular telephone and in a battery cartridge.
Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.